1. Field of Invention
The invention relates to a fan system and a power monitoring apparatus thereof, and in particular to a fan system and a power monitoring apparatus thereof capable of preventing an instantaneous voltage or current variation from influencing a fan assembly.
2. Related Art
The desired functionality of electronic apparatuses is getting ever broader and more powerful, and the array of various accessory apparatuses is also increasing. Therefore, as circuits become increasing and more complicated, the power management device has become an indispensable element of electronic apparatuses, for preventing trace short-circuits from damaging expensive equipments. Fans, fan modules and motors are included in this trend.
When a fan or motor operates, the circuit of the fan or the motor can be impacted by an instantaneous current or voltage that causes the current or voltage to shut down and damages the circuit or the motor of the fan. Also, over-heating can occur because the fan stops operating while the electronic apparatus normally cooled by the fan continues to operate. In order to solve the above-mentioned problems, an over-voltage apparatus or an over-current monitoring apparatus is usually used in a fan to protect the electronic apparatus or the fan from being influenced by instantaneous over-current or instantaneous over-voltage events.
As shown in FIG. 1, a conventional over-voltage apparatus 1 is electrically connected with a motor M of a fan and includes two resistors R and R′ and a processor 11 electrically connected with the resistors R and R′, and a default voltage is set. The over-voltage apparatus 1 operates as follows. An external voltage signal Vin is divided by the resistors R and R′ to generate a voltage divided signal Vs, which is transferred to the processor 11. The processor 11 compares the voltage divided signal Vs with the default voltage. When the voltage divided signal Vs is higher than the default voltage, the processor 11 outputs a control signal Sc to the motor M so as to decrease the rotating speed of the motor M.
As shown in FIG. 2, a conventional over-current apparatus 2, electrically connected with a motor M of a fan, includes a sensing resistor Rs and a controller 21. The controller 21 is electrically connected with the sensing resistor Rs and sets a default current. The over-current apparatus 2 operates as follows. The sensing resistor Rs senses an external voltage signal Vin to generate a current signal Is, which is transferred to the controller 21. The controller 21 compares the current signal Is with the default current. When the current signal Is is greater than the default current, the controller 21 outputs a control signal Sc to the motor M so as to reduce the rotating speed of the motor M.
However, the fan using the over-voltage apparatus 1 only can detect an over-voltage condition but cannot immediately detect an instantaneous voltage variation and thus cannot effectively protect the fan. On the other hand, due to the slow response speed of detection, the fan using the over-current apparatus 2 cannot instantaneously suppress the inrush current, which is generated because the voltage changes, and thus the fan assembly tends to be damaged easily. Therefore, neither the over-voltage apparatus 1 nor the over-current apparatus 2 can immediately detect the instantaneous current or voltage variation, and thus both of them cannot effectively protect the fan. This may ultimately shorten the lifetime of the fan.
Consequently, it is an important subject of the invention to provide a fan system capable of immediately detecting instantaneous voltage or current variation and a power monitoring apparatus so as to protect the fan assembly and thus to lengthen the lifetime of the fan system.